1. Field of the Invention
The present invention generally relates to optical switches used in optical communications, and more particularly to a non-mechanical optical switch.
2. Description of Prior Art
For purposes of convenience and economy, it is often desirable to employ switches in optical networks, so that either a single optical signal can be shared between two or more users or a single user can choose from a variety of optical signals without the added expense and complexity of installing additional hardware.
Optical switches can be classified as mechanical optical switches or as non-mechanical optical switches. Mechanical optical switches realize changes in lightpaths by moving optical fibers or elements using principles of mechanics or electromagnetism.
Referring to FIGS. 6a and 6b, U.S. Pat. No. 5,724,165 discloses a conventional optical switch 40 which includes two input ports 41, 42, three birefringent elements 401, 403, 407, two polarization rotator arrays 402, 406, a polarization beamer splitter (PBS) 404, a prism 405 and two output ports 43, 44. The optical switch 40 realizes optical switching by rotating the two polarization rotator arrays 402, 406. Particularly referring to FIG. 6a, when the two polarization rotator arrays 402, 406 are in a first state, input light from the first input port 41 successively transmits through the first birefringent element 401, the first polarization rotator array 402, the second birefringent element 403, the prism 405, the second polarization rotator array 406 and the third birefringent element 407, and outputs through a second output port 44. Input light from the second input port 42 successively transmits through the first birefringent element 401, the first polarization rotator array 402, the second birefringent element 403, the prism 405, the PBS 404, the second polarization rotator array 406 and the third birefringent element 407, and outputs through a first output port 43. Referring to FIG. 6b, the two polarization rotator arrays 402, 406 are in a second state, and input light from the first input port 41 successively transmits through the first birefringent element 401, the first polarization rotator array 402, the second birefringent element 403, the PBS 404, the second polarization rotator array 406 and the third birefringent element 407, and outputs through the first output port 43. Input light from the second input port 42 successively transmits through the first birefringent element 401, the first polarization rotator array 402, the second birefringent element 403, the prism 405, the second polarization rotator array 406 and the third birefringent element 407, and outputs through the second output port 44.
However, the conventional optical switch has many shortcomings. First, the optical switch 40 realizes optical switching by rotating the polarization rotator arrays 402, 406, and thus complex mechanical mechanisms are required for working the optical switch 40. Second, the optical switch 40 has degraded optical performance, including a large optical attenuation, since the light has to pass through too many optical elements in traveling from the input port to the output port.
An optical switch having good optical performance which requires no moving optical elements is desired.